IEA HPP Annex 28 Calculation method

1. IEA HPP Annex 28Calculation method Workshop IEA HPP Annex 28 8th International Heat Pump Conference, Las Vegas, 30 May 2005 Carsten Wemhöner, Operating Agent IEA HPP Annex 28 Institute of Energy, University of Applied Sciences Basel

2. Outline of the presentation • Objectives • Principle of the calculation • Extension to combined systems • Simplifications, calculations steps and input data

3. Objectives of the calculation method • Transparent • no correction factors as far as possible • Easy-to-use • “hand calculation”, no extensive computer application or simulation • suited for standards • Based on publicly available data • standard testing results • component characteristics from technical data sheets • Applicable to the majority of systems on the market

4. Calculation method – basic situation • Output capacity and efficiency (COP) strongly dependent on source and sink temperature and changes over the operation range • Output capacity and efficiency (COP) are known at defined testing points (from standard component testing) • Meteorological data available for evaluation of the source temperature • Controller settings available for the characterisation of the sink temperature • Annual energy requirement for space heating and domestic hot water are known from standard calculations (building regulations)

5. Principle of the calculation method Meteo data processing • Annual frequency of the ambient dry bulb air temperature • Cumulative annual frequency of the ambient dry bulb air temperature ambient dry bulb temperature [°C]

6. Design indoor temperature Upper ambient temperature for heating 3, upper 3 OP3 3, lower OP2 design outdoor temperature OP1 Principle of the calculation method Bin distribution • Operation conditions at the operating points valid for the entire bin • Bins should have connection to available information on the heat pump characteristic • Operating point in the centre of the bin • Bin limits between operating points • Conclusion: ambient dry bulb temperature [°C]

7. Performance factor at operating point • Efficiency values from standard testing valid for the whole bin • COP interpolated for the conditions at the operating point Qnet,i Qnet,i Qnet,i • Further system losses • Storage losses PFi = Qnet,i + Qloss,i + Eaux,i COPi COPi • Additional electrical auxiliary expense • heat pump auxiliaries not considered in the COP boundary (e.g. brine source pump) • Circulation pumps • Control only in times when heat pumps is not running

8. Design indoor temperature Upper ambient temperature for heating • Heating degree hours= 3, upper 3 OP3 HP3 3, lower OP2 HP2 a design outdoor temperature HP1 OP1 dt ID Principle of the calculation method Energy requirement • Area of the bin (area between cumulative frequency and indoor design temperature) corresponds to energy requirement • Energy requirement in the bin corresponds to difference of cumulative heating degree hours at bin limit • Measure for the energy requirement:Heating degree hours(HDH) • Relative energy requirement in the bin corresponds to ratio of bin areas(weighting factor) • Operation conditions at operating point valid for the entire bin ambient dry bulb temperature [°C]

9. Seasonal performance factor of heat pump • Seasonal performance by summation over all bins • Electricity input can be expressed with performance factor iQnet,i Qnet 1 SPFhp = wi iEi Qnet,i i ·Qnet PFi • Ratio between bin heat requirement and total heat requirement can be expressed by weighting factor

10. Design indoor temperature Upper ambient temperature for heating BU OP3 HP3 Balance point temperature OP2 low temperature cut-out HP2 BU design outdoor temperature HP1 HP1 OP1 BU Principle of the calculation method Back-up energy • Alternate operation modeheat pump is switched- off at balance point • Parallel operation modeheat pump runs through • Mixed operation mode heat pump is switched- off at low temperature cut-out • Operation of the back-up heating defined by • Operation mode • Balance point temperature • Low temperature cut-out ambient dry bulb temperature [°C]

11. Seasonal performance factor of heating mode • Overall performance of heat pump and back-up heating by weighting with delivered energy fractions Qhp Qnet + Qbu SPFh = Qbu Ehp Qhp + Ebu + bu SPFhp

12. Design indoor temperature OP4 W4 OP3 HP W3 Balance point temperature HP W2 design outdoor temperature W1 BU Principle of the calculation method Domestic hot water Upper ambient temperature for heating • Evaluation of heat pump characterstic based on DHW-testing • Approach: Daily tapping profile • Hot water energy dependent on bin time • Back-up energy of domestic hot water mode is determined by temperature level (operation limit heat pump) • Combination of different operation modes by weighting with the respective energy fractions OP2 OP1 HP ambient dry bulb temperature [°C]

13. Extension to combined systems Alternate combined operating systems (heat pump switched): • Result from testing:characteristic does not change significantly • Calculation of space heating and domestic hot water part • Superposition of single operation modes with weighting of energy fractions

14. Extension to combined systems Simultaneous combined operating systems (heat extraction): • Characteristic in simultaneous operation changes significantly! • Three operation modes have to be considered: • Single space heating (e.g. winter operation, DHW storage entirely loaded) • Single domestic hot water (e.g. summer operation) • Simultaneous space heating and domestic hot water (SH and DHW demand) • Fraction of operation in each operation mode by evaluating the running time

15. Extension to combined systems • Running time t:produced heat/output capacity • Maximum running time in combined operation • If tSH > tDHW => tcombi = tDHW => DHW operation limiting factor for simultaneous operation • If tDHW > tSH => tcombi = tSH => SH operation limiting factor for simultaneous operation • Either space heating (intermediate season) or DHW (winter) could be the limiting factor for combined operation • Maximum value may not be reached due to control effects and not necessarily simultaneous load requirement

16. Overall seasonal performance factor • As in the alternate case the overall seasonal performance of simultaneous operation is calculated • Weighting of the performance factors of the operation modes • with the respective energy fraction Qh + QDHW SPF = Qcombi Qh QDHW + + SPFcombi SPFDHW SPFh

17. Assumptions/Simplifications • Main impact on space heating is outside temperature • Effects of intermittent heating included in the calculation of energy requirement (EN ISO 13790) • defrosting considered in the heat pump characteristic (e.g. EN 14511) • Domestic hot water requirement constant over the year (daily consumption) • Control effect cannot entirely be described but is reflected by standard situations

18. Calculation steps • Determination of energy requirement per bin • Determination of fraction by back-up energy (bivalent operation) • Interpolation of output capacity and COP for source and sink temperature • Correction for part load operation • Evaluation of running time in different operation modes • Calculation of auxiliary energy • Calculation of generator losses (recoverable/recovered) • Calculation of total energy input, system seasonal performance

19. Input data • Data of the site • Meteorological data (i.e. hourly values of the outside temperature, irradiation) • Source temperature (e.g. outside air, ground, ground water etc.) • Energy Requirements • Space heating energy requirement • Domestic hot water energy requirement • Heat pump • Type of the heat pump (e.g. brine-to-water, outside-air-to-water etc.) • Heat pump characteristic (standard testing, e.g. EN 14511, ASHRAE 116 etc.) • Operation limits

20. Input data • System components characteristics • Installed storages (heating buffer, domestic hot water) • Back-up generators (electrical, fossil) • Domestic hot water operation (independent/alternate/combined) • Nominal power of auxiliaries (pumps, fans, control…) • System design • Controller settings (heating characteristic curve, upper temperature limit for heating) • Balance point (input or based on design heat load)

21. Thank you for your attention!